Answer:
wind is air in motion
Explanation:
In our present understanding of the nature of the Universe and the Laws of Physics, matter (anything with mass) is made up of elementary particles. For the most part, we have given names to groups of such particles: electron, neutron, proton, atom, molecule. And, we have identified various "states" the matter can be in, presumably depending on the motions of those particles relative to each other and their surroundings. Such states include solid, liquid, gas, plasma.
The atmosphere is mostly made up of gases of various kinds. The most prevalent are nitrogen and oxygen, each consisting of molecules of two atoms of the same kind. There are numerous other gases in the atmosphere, along with small amounts of matter in other states.
When the constituents of the atmosphere move in one direction more than any other, we call that a <em>current</em>. In air (the atmosphere), such currents are called wind, thermals, updrafts, downdrafts, tornadoes, hurricanes, and a variety of other names. In general, they are a consequence of a pressure difference between one part of the atmosphere and another.
Just as ketchup squirts from a bottle when you apply pressure to it, air moves from a place of high pressure to one of low pressure. In the case of wind in the atmosphere, the path it takes is not always direct, but is modified by geography and the rotation of the earth. (You may have some sense of this modification of the path if you've ever tried to play catch on a moving merry-go-round.)
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The pressure differences that give rise to air currents most often are a result of temperature differences. Different pars of the earth are heated and cooled at different rates by the sun, by radiation into space, and by transformations in the state of water in the atmosphere.
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There are currents in all sorts of places, involving matter of all types. There are currents of water in rivers, lakes, seas, oceans. There are currents of ice in ice packs (Greenland and Antarctica, for example). There are current of electrons in electric wires. There are currents of rock in the middle of the earth.
